Cloning Flashcards
What is a clone?
It is the offspring produced as a result of cloning
What is cloning?
A wa of producing offspring by asexual reproduction
What is asexual reproduction?
The production of genetically identical offspring from a single parent
What is reproductive cloning?
The process of producing a genetically identical copy (a clone) of an entire organism
What is vegetative propagation?
- The artificial production of natural clones for use in horiculture and agriculture
- It is also referred to as natural cloning
What is a perennating organ?
- Perennating organs enable plants to survive adverse conditions
- They contain stoed food from photosynthesis and can remain dormant in soil
- Vegetative propagation involves perennating organs, as the store food can be used to provide the energy for cloning
- They provide a way of surviving from one growing season to the next
What are some examples of natural plant cloning?
- Bulbs (e.g. daffodil) => the leaf bases swell with stored food from photosynthesis. Buds form internally which develop into new shoots and new plants in the next growing season
- Runners (e.g. a strawberry or spider plant) => a lateral stem grows away from the parent plant and roots develop where the runner touches the ground. A new plant develops - the runner eventually withers away leaving the new individual independent
- Rhizomes (e.g. marram grass) => a rhizome is a specialised horizontal stem running underground, often swollen with stored food. Buds develop and form new vertical shoots which become independent plants
- Stem tubers (e.g. potato) => the tip of an underground stem becomes swollen with stored food to form a tuber or storage organ. Buds on the storage organ develop to produce new shoots (e.g. the ‘eyes’ on a potato)
What is horiculture?
It is the art and science of growing ornamental plants, fruits, vegetables, flowers, trees and shrubs
What is agriculture?
It is the science or practice of farming, including cultivation of the soil of the growing of crops and the rearing of anials to produce food, wool and other products
How is the production of natural clones exploited in horiculture?
- Natural plant cloning is exploited in horiculture by farmers and gardeners to produce new plants
- Splitting up bulbs, removing young plants from runners, and cuting up rhizomes all increase plant numbers cheaply, and the new plants have exactly the same genetic characteristics as their parents
What are cuttings? And how are they used in horiculture?
- Cuttings are short sections of stems are taken and planted either directly in the ground or in pots
- Rooting hormone is often applied to the base of a uctting to encourage the growth of new roots
How can the success rate of taking cutting be increased?
- Use a non-flowering stem
- Make an oblique (diagnol) cut in the stem
- Use hormone rooting powder
- Reduce leaves to two or four
- Keep cutting well watered
- Cover the cutting with a plastic bag for a few days
What are some examples of crops that are propagated by cloning?
- Bananas
- Sugar cane
- Sweet potatoes
- Cassava
- Coffee
- Tea bushes
What are the advantages of propagating crops by cloning?
- The time from planting to cropping is much reduced => process is much faster
- Guarantees quality of plants => taking cutting from good stock, so you get genetically identical offspring that crop well
What are the disadvantages of propagating crops by cloning?
Lack of genetic variation => if there is a new disease or pest or climate changes, all clones will die
What is tissue culture?
Tissue culture is a method of biological research in which fragments of tissue from an animal or plant are transferred to an artificial environment in which they can continue to survive and function
What is micropropagation?
Micropopagation is the process of making very large numbers of gentically identical offspring from a single parent plant using tissue culture techniques
What is an explant?
It is a small piece of a plant
What is a callus?
A massive growth of cells or disorganised plant cell massess (calli) produced from a single differentiated cell totipotent and able to regenerate a whole plane
When is micropropagation used?
It is used to produce plants when a desirable plant:
- Does not readily produce seeds
- Doesn’t respond well to natural cloning
- Is very rare
- Has been genetically modified or selectively bred with difficulty
- Is required to be ‘pathogen-free’ by growers e.g. strawberries, bananas and potatoes
What is the process of micropropagation and tissue culture?
- Take a small sample of tissue from the plant you want to clone - the meristem tissue from shoot tips and axial buds is often dissected
out in sterile conditions to avoid contamination by fungi and bacteria. This tissue is usually virus-free. - The sample is sterilised, usually by immersing it in sterilising agents such as bleach, ethanol, or sodium dichloroisocyanurate. The latter does not need to be rinsed off which means the tissue is more likely to remain sterile. The material removed from the plant
is called the explant. - The explant is placed in a sterile culture medium containing a balance of plant hormones (including auxins and cytokinins) which stimulate mitosis. The cells proliferate, forming a mass of
identical cells known as a callus. - The callus is divided up and individual cells or clumps from the callus are transferred to a new culture medium containing a different mixture of hormones and nutrients which stimulates the development of tiny, genetically identical plantlets.
- The plantlets are potted into compost where they grow into small plants.
- The young plants are planted out to grow and produce a crop.
What are the advantages of micropropagation?
- Micropropagation allows for the rapid production of large
numbers of plants with known genetic make-up which will yield good crops. - Culturing meristem tissue produces disease-free plants.
- It makes it possible to produce viable numbers of plants after genetic modification of plant cells.
- It provides a way of producing very large numbers of new plants
which are seedless and therefore sterile to meet consumer tastes (e.g., bananas and grapes). - It provides a way of growing plants which are naturally relatively infertile or difficult to grow from seed (e.g., orchids).
- It provides a way of reliably increasing the numbers of rare or endangered plants.
What are the disadvantages of micropropagation?
- It produces a monoculture - many plants which are genetically identical - so they are all susceptible to the same diseases or changes in growing conditions.
- It is a relatively expensive process and requires skilled workers.
- The explants and plantlets are vulnerable to infection by moulds and other diseases during the production process.
- If the source material is infected with a virus, all of the clones will also be infected.
- In some cases, large numbers of new plants are lost during the process.
What are some examples of cloning in invertebrates?
- Flatworms and sponges fragment and form new identical animals as part of their normal reproductive process, all clones of the orginal
- Hydra produce small ‘buds’ on the side of their body which develop into genetically identical clones
What is the reason for this use of artificial twinning?
It is used by the farming community to produce the maximum offspring from particularly good dairy or beef cattle or sheep
What are the stages of artificial twinning in cattle?
- A cow with desirable traits is treated with hormones as she super-ovulates, releasing more mature ova than normal
- The ova may be fertilised naturally, or by artificial insemination, by a bull with particularly good traits. The early embryos are gently
flushed out of the uterus - Alternatively, the mature eggs are removed and fertilised by top-quality bull semen in the lab
- Usually before or around day six, when the cells are still totipotent, the cells of the early embryo are split to produce several smaller embryos, each capable of growing on to form a healthy full-term calf
- Each of the split embryos is grown in the lab for a few days to ensure all is well before it is implanted into a surrogate mother. Each embryo is implanted into a different mother as single pregnancies carry fewer risks than twin pregnancies
- The embryos develop into foetuses and are born normally, so a number of identical cloned animals are prodced by different mothers
What does SCNT stand for?
- Somatic cell nuclear transfer
- It is also known as reproductive cloning
What is the process of SCNT?
1) The nucleus is removed from a somatic cell of an adult animal
2) The nucleus is removed from a nature ovum harvested from a different female animal of the same species (it is enucleated)
3) The nucleus from the adult somatic cell is placed into the enucleated ovum and given a mild electric shock so it fuses and begins to divide. In some cases, the nucleus from the adult cell is not removed - it is simply placed next to the enucleated ovum and the two cells fuse (electrofusion) and begin to divde under the influence of the electric current
4) The embyro that develops is transferred into the uterus of a third animal, where it develops to term
5) The new animal is a clone of the animal from which the original somatic cell is derived, although the mitochondrial DNA will come from the egg cell
What are the advantages of animal cloning?
- Artificial twinning enables high-yielding farm animals to produce many more offspring than normal reproduction
- Artificial twinning enables the success of a site (the male animal) at passing on desirable genes to be determined. If the first cloned embryo results in a successful breeding animal, more identical animals can be reared from the remaining frozen clones. The use of meat from animals born to a cloned parent is now permitted in the US
- SCNT enables GM embryos to be replicated and to develop, giving many embryos one engineering procedure. It is an important process in pharming - the production of theraputic human proteins in the milk of genetically engineered farm animals, such as sheep and goats
- SCNT enables scientists to clone specific animals e.g. replacing specific pets or cloning to-class race horses. Pet cats and dogs have been cloned in the US at great expense
- SCNT has the potential to enable rare, endangered, or even extinct animals to be reproduced. In theory, the nucleus from dried or frozen tissue could be transferred to the egg of a similar living species and used to produce clones of species that have been dead for a long time
What are the disadvantages of animal cloning?
- SCNT is a very inefficient process - in most animals it takes many eggs to produce a single cloned offspring
- Many cloned animal embryos fail to develop and miscarry or produce malformed offspring
- Many animals produced by cloning have shortened lifespans, although clone mice have now been developed which live a normal two years
- SCNT has been relatively unsuccessful so far in increasing the population of rare organisms or allowing extinct species to be brought back to life
